Power supply having reduced-power mode

ABSTRACT

A power supply of one embodiment of the invention is disclosed that includes a conversion mechanism and a feedback mechanism. The conversion mechanism is to control conversion of a first direct current (DC) signal from to a second DC signal provided to an electronic device by switching the first DC signal to vary the second DC signal. The feedback mechanism is to cause the switching control mechanism to operate in a nominal-power mode or a reduced-power mode according to a control signal received from the electronic device. The conversion mechanism is caused in the reduced-power mode to lessen at least one of the duty cycle and the frequency at which the first DC signal is switched until the voltage of the second DC signal decays to a first voltage level.

BACKGROUND

Many electronic devices, such as computer peripherals like printers, canconsume large amounts of power when they are on, even when they are idleand not currently performing functional tasks. For example, when inkjetand laser printers and other types of image-forming devices are on, theymay have to consume large amounts of power when idle so that when calledupon to print, the printers can quickly begin printing. Other electronicdevices, such as other types of computer peripherals and other types ofelectronic devices, may similarly use large amounts of power when idle.

However, individuals, organizations, and governments have recently begunto question the power consumption used by such devices, especially whenthey are idle and not otherwise performing functional tasks. Individualsand organizations are looking for greater energy efficiency to lowertheir electrical bills. Governments are looking for greater energyefficiency so that the need to build more power plants is reduced, andto avoid brownout and blackout scenarios when power plants are operatingat peak capacity. This is especially the case in extremely hot weather,when air conditioners may be running constantly, and utilizing morepower than they otherwise would.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings referenced herein form a part of the specification.Features shown in the drawing are meant as illustrative of only someembodiments of the invention, and not of all embodiments of theinvention, unless otherwise explicitly indicated.

FIG. 1 is a diagram of an embodiment of a power supply, according to anembodiment of the invention.

FIGS. 2A and 2B are graphs of example waveforms within the power supplyof FIG. 1 in full- or normal-power mode, and in low-power mode,respectively, according to an embodiment of the invention.

FIG. 3 is a flowchart of a method, according to an embodiment of theinvention.

FIG. 4 is a diagram of an embodiment of a power supply in more detailthan but consistent with the power supply of FIG. 1, according to anembodiment of the invention.

FIG. 5 is diagram of the feedback mechanism of FIG. 4 in more detail,according to an embodiment of the invention.

FIGS. 6A and 6B are diagrams of embodiments of an electronic device,according to varying embodiments of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description of exemplary embodiments of theinvention, reference is made to the accompanying drawings that form apart hereof, and in which is shown by way of illustration specificexemplary embodiments in which the invention may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the embodiments of the invention. Otherembodiments may be utilized, and logical, mechanical, and other changesmay be made without departing from the spirit or scope of the appendedclaims. The following detailed description is, therefore, not to betaken in a limiting sense, and the scope of the present invention isdefined only by the appended claims.

Power Supply and Method

FIG. 1 shows an embodiment of a power supply, power supply 100,according to an embodiment of the invention. The power supply 100 is foran electronic device, not depicted in FIG. 1, and may be internal orexternal to the electronic device. The electronic device may be animage-forming device, such as an inkjet-printing device or alaser-printing device, or another type of device other than animage-forming device. The power supply 100 specifically receives a firstalternating current (AC) signal from a power source 112, such as a walloutlet, as indicated by the arrow 120, and converts it to a first directcurrent (DC) signal, as indicated by the arrow 108, which is thenconverted to a second DC signal, as indicated by the arrow 114, toprovide to the electronic device. The difference between the first DCsignal and the second DC signal is that the first DC signal may not beregulated, and may not have the proper voltage level for the electronicdevice to operate, as compared to the second DC signal. The power supply100 operates in a full-power, or normal-power or nominal-power, mode, inwhich the second DC signal is provided to the electronic device at afull, normal, or nominal level while the electronic device is activelyoperating or functioning, and in a low-power mode, which may moregenerally be referred to as a reduced-power mode, in which second DCsignal is provided at a lower current, voltage, and/or power level whilethe electronic device is idling, or not actively operating orfunctioning.

The power supply 100 includes an AC-DC mechanism 102, a DC-DC mechanism104, a switching control mechanism 106, and a feedback mechanism 110.The AC-DC mechanism 102 receives the first AC signal from the powersource 112 and converts the first AC signal to the first DC signal, andincludes those components that enable it to receive the first AC signalfrom the power source 112 and convert the first AC signal to the firstDC signal. The DC-DC mechanism 104 converts the first DC signal to thesecond DC signal, provides the second DC signal to the electronicdevice, as indicated by the arrow 114, and includes those componentsthat enable it to convert the first DC signal to the second DC signaland provide the second DC signal to the electronic device. The DC-DCmechanism 104 converts the first DC signal to the second DC signal byswitching by switching the first DC signal high and low, and iscontrolled by the switching control mechanism 106.

The switching control mechanism 106 may also be referred to as aconversion mechanism. The switching control mechanism 106 includes thosecomponents that enable it to control the conversion of the first DCsignal to the second DC signal, by switching the first DC signal suchthat the second DC signal is varied, as indicated by the arrow 118. Thefeedback mechanism 110 causes the switching control mechanism 106 tooperate either in the full-power mode or the low-power mode, accordingto a control signal received from the electronic device, as indicated bythe arrow 116. The feedback mechanism 110 therefore contains thecomponents that enable it to cause the switching control mechanism 106to operate in the full-power mode or the low-power mode, based on thecontrol signal. It is noted that receiving of the control signalencompasses deriving the control signal from another type of signal, aswell as receiving a direct signal. Furthermore, the utilization of thecontrol signal allows for the anticipation of load changes by the powersupply 100, based on the information presented by the electronic deviceas encompassed within the control signal.

FIGS. 2A and 2B show graphs 200 and 250 of the waveforms provided by theswitching control mechanism 106 and the DC-DC mechanism 104, in thefull-power mode and the low-power mode, respectively, according to anembodiment of the invention. The y-axis 202 of the graphs 200 and 250denotes voltage as a function of time on the x-axis 204. In thefull-power, or normal-power, mode, the signal output by the switchingcontrol mechanism 106 and input by the DC-DC mechanism 104, asidentified by the arrow 118 in FIG. 1, is the control waveform 206. Thecontrol waveform 206 is in particular an example waveform that is at afifty-percent duty cycle, and may in other embodiments be a differenttype of waveform. The waveform of the second DC signal output by theDC-DC mechanism 104, as identified by the arrow 114 in FIG. 1, in thefull-power mode is the output waveform 208. The output waveform 208 is arudimentary linear depiction of a decaying voltage, and may berepresented in other manners, such as an exponential decay. In thelow-power mode, the waveform identified by the arrow 118 in FIG. 1 isthe control waveform 216, whereas the waveform identified by the arrow114 in FIG. 1 is the output waveform 218.

In the full-power mode, the switching control mechanism 106 is caused bythe feedback mechanism 110 to switch the first DC signal at a duty cycleand at a frequency, such that the voltage of the output waveform 208 ofthe second DC signal fluctuates between a voltage level 210 and avoltage level 212, and has an average voltage level 214. When thevoltage of the output waveform 208 increases to the level 212, thecontrol waveform 206 changes state, so that the voltage of the outputwaveform 208 decreases. When the voltage of the output waveform 208decays to the level 210, the control waveform 206 goes high, so that thevoltage of the output waveform 208 increases. The rate at which thecontrol waveform 206 switches high and low is the frequency, and theratio between the control waveform 206 being high and the total high andlow portions of the control waveform 206 is the duty cycle. The outputwaveform 208 is a regulated DC signal, so that the electronic device canoperate when actively functioning.

In the low-power mode, the switching control mechanism 106 is caused bythe feedback mechanism 110 to switch the first DC signal at a differentfrequency and/or duty cycle, such that the voltage of the outputwaveform 218 of the second DC signal fluctuates between a voltage level224 and a voltage level 220, and has an average voltage level 222. Whenthe voltage of the output waveform 218 increases to the level 224, thecontrol waveform 206 goes low, so that the voltage of the outputwaveform 218 decreases. That is, the feedback mechanism 110 causes theswitching control mechanism 106 to lessen switching the first DC signal,by lessening the frequency and/or the duty cycle of the switching. InFIG. 2B, this lessening of switching is shown as a complete stoppage ofswitching, whereas in other embodiments, lessening of switching mayinstead reduce the frequency and/or duty cycle of the switching. Whenthe voltage of the output waveform 218 decreases or decays to the level220, the control waveform 216 again resumes switching at the duty cycle,in what can be referred to as a burst mode, so that the voltage of theoutput waveform 218 increases. The duty cycle at which the controlwaveform 216 resumes switching may be the same as the duty cycle of thecontrol waveform 206, or may be a higher efficiency duty cycle. Havingthe duty cycle at which the control waveform 216 resumes switching be ofhigher efficiency than the duty cycle of the control waveform 206 lowersaverage power loss, which increases efficiency of the power supply 100.Furthermore, the voltage of the output waveform 218 may not need to beas tightly regulated as the output waveform 208, since the electronicdevice is idling.

FIG. 3 shows a method 300 for performance by the power supply 100 ofFIG. 1 in accordance with the graphs 200 and 250 of FIGS. 2A and 2B,according to an embodiment of the invention. The first AC signal fromthe power source 112 is converted to the first DC signal, and the firstDC signal is converted to the second DC signal (302). The second DCsignal is provided to the electronic device (304), as indicated by thearrow 114. The power supply 100 receives a control signal from theelectronic device to operate in the low-power mode (306). As a result,the first DC signal is switched at a duty cycle and at a frequency untilthe voltage of the second DC signal reaches a first voltage level, suchas the voltage level 224 (308). Once the voltage of the second DC signalreaches the first voltage level, switching of the first DC signal isstopped, or lessened, until the voltage of the second DC signal decaysto a second voltage level, such as the voltage level 220 (310). Theelectronic device is thus idling in the low-power mode (312).

If a control signal is not received from the electronic device to switchoperation of the power supply 100 to the full-power mode (314), 308,310, and 312 are repeated. Once a control signal is received from theelectronic device to switch operation of the power supply 100 to thefull-power mode (314), then the first DC signal is switched at a dutycycle and at a frequency so that the voltage of the second DC signalfluctuates between a third voltage level and a fourth voltage level(316). The duty cycle and/or the frequency at which the first DC signalis switched in the full-power mode can be higher than the duty cycleand/or the frequency at which the first DC signal is switched in thelow-power mode. The third voltage level may be the voltage level 212,and the fourth voltage level may be the voltage level 210. Theelectronic device is thus actively functioning, or operating, in thefull-power, or normal-power mode (318). If a control signal is notreceived from the electronic device to switch operation of the powersupply 100 back to the low-power mode (320), then 316 and 318 arerepeated. Once a control signal is received from the electronic deviceto switch operation of the power supply 100 back to the low-power mode(320), the method 300 is performed again, starting at 308.

It is noted that the method 300 of FIG. 3 is described such that theelectronic device idles in the low-power mode, in 312, before itactively functions in the full-power mode, in 318. However, in adifferent embodiment of the invention, the electronic device mayactively function in the full-power mode before idling in the low-powermode. That is, after performing 304, the method 300 may in anotherembodiment of the invention next perform 316, so that the electronicdevice actively functions in the full-power mode before entering thelow-power mode, as can be appreciated by those of ordinary skill withinthe art.

Power Supply in Detail and Electronic Device

FIG. 4 shows the power supply 100 such that it is more detailed than butconsistent with the embodiment of FIG. 1, according to an embodiment ofthe invention. The power supply 100 again converts a first alternatingcurrent (AC) signal from the power source 112, as indicated by the arrow120, to a second direct current (DC) signal provided to an electronicdevice, as indicated by the arrow 114. The power supply 100 is operablein a normal-power, or full-power mode, and a low-power mode, dependingon a control signal received from the electronic device, as indicated bythe arrow 116. For example, asserting the control signal, such that thecontrol signal is present, may indicate to the power supply 100 tooperate in the low-power mode, and not asserting the control signal,such that it is absent, may indicate to the power supply 100 to operatein the normal-power mode.

The power supply 100 includes the AC-DC mechanism 102, the DC-DCmechanism 104, the switching control mechanism 106, and the feedbackmechanism 110. The AC-DC mechanism 102 includes a full-wave bridgerectifier 402, connected to the positive and negative terminals of thepower source 112. The power source 112 may also include a groundterminal connected to ground. The negative side of the rectifier 402 maybe connected to ground, whereas the positive side of the rectifier 402is connected to a regulating capacitor 408.

The DC-DC mechanism 104 includes a transistor 410, a resistor 412connected in series between the transistor 410 and a ground 418, whichmay be Earth ground or another type of ground, and a transformer 414.The transformer 414 converts the first DC signal received from the AC-DCmechanism 102 on one side to the second AC signal on its other side,which is also connected to a ground 416, which may be Earth ground oranother type of ground. The transistor 410 is controlled by theswitching control mechanism 106. That is, the switching controlmechanism 106 controls switching of the first DC signal provided to thetransformer 414 high and low. The switching control mechanism 106 may bea ringing choke converter (RCC), a pulse-width modulated (PWM) switcher,or may be a switching control mechanism that utilizes another type ofswitching topology.

The DC-DC mechanism 104 further includes a half-wave rectifier 420, anda regulating capacitor 424, which generate the second DC signal from thesecond AC signal. The capacitor 424 is connected in parallel between thesecond DC signal and a ground input of the electronic device. It isnoted that the utilization of the half-wave rectifier 420 and theregulating capacitor 424 is an example topology that can be employed togenerate the second DC signal from the second AC signal. In otherembodiments of the invention, other topologies may be used to generatethe second DC signal from the second AC signal. The second DC signal isindicated by the arrow 114, whereas the ground input is indicated by thearrow 428, where the ground input is connected to a ground 406, such asan Earth ground or another type of ground. The ground input, and thusone side of the capacitor 424, is also connected to a pull-down 426. TheDC-DC mechanism 104, besides providing the second DC signal to theelectronic device, also provides a measure of the second DC signal tothe feedback mechanism 110, due to its connection thereto. This measureof the second DC signal enables the feedback mechanism 110 to be able todetermine the type of feedback signal to provide to the switchingcontrol mechanism 106, in order for the switching control mechanism 106to appropriately control switching of the first DC signal by the DC-DCmechanism 104.

The feedback mechanism 110 includes a modal mechanism 430 and acomparing mechanism 432. The comparing mechanism 432 compares thevoltage of the second DC signal provided to the electronic device by theDC-DC mechanism 104 to the voltage levels 210 and 212 of FIG. 2A. Inresponse, the comparing mechanism 432 generates a feedback signal tocause the switching control mechanism 106 to switch the first DC signallow upon the voltage of the second DC signal reaching the voltage level212 so that the second DC signal decreases, and to switch the first DCsignal high upon the voltage of the second DC signal reaching thevoltage level 210 so that the second DC signal increases. The comparingmechanism 432, without input from the modal mechanism 430, enables theswitching control mechanism 106 to operate the DC-DC mechanism 104 inthe normal-power, or full-power mode.

The modal mechanism 430 effectively skews comparison of the voltage ofthe second DC signal to the voltage levels 210 and 212 of FIG. 2A, byusing in one embodiment a time-voltage sensitive reactive device (513),in response to receiving the control signal from the electronic device,such that the power supply 100 is to operate in the low-power mode. As aresult, the comparing mechanism 432 instead is effectively caused by themodal mechanism 430 to compare the voltage of the second DC signal tothe voltage levels 220 and 224. In response, the comparing mechanism 432is caused to generate a feedback signal to cause the switching controlmechanism 106 to switch the first DC signal low upon the voltage of thesecond DC signal reaching the voltage level 224, so that the DC signaldecreases or decays, and to switch the first DC signal at a duty cycleand at a frequency upon the voltage of the second DC signal decreasingto the voltage level 220 so that the second DC signal increases.

In other words, the modal mechanism 430 essentially passes through themeasure of the second DC signal to the comparing mechanism 432 withoutmodification, to allow the switching control mechanism 106 to operate inthe full-power mode. The modal mechanism 430 also essentially modifiesthe second DC signal before passing a skewed measure of the second DCsignal to the comparing mechanism 432 to cause the switching controlmechanism 106 to operate in the low-power mode. When the control signalis not asserted by the electronic device, such that it is absent, themodal mechanism 430 passes through the second DC signal to the comparingmechanism 432, and when the control signal is asserted by the electronicdevice, such that it is present, the modal mechanism 430 modifies the DCsignal before passing it to the comparing mechanism 432. It is notedthat the skewing of the second DC signal to comparing mechanism 432 inthe low-power mode is voltage-time sensitive. This allow for higherefficiency to be realized, as well as power utilization by the load tobe lessened.

FIG. 5 shows a diagram of the modal mechanism 430 and the comparingmechanism 432 of the feedback mechanism 110 in more detail, according toan embodiment of the invention. As indicated by the incoming arrow 516,both the comparing mechanism 432 and the modal mechanism 430 receive ameasure of the second DC signal provided to the electronic device, fromthe DC-DC mechanism 104. The comparing mechanism 432 provides a feedbacksignal 508 to the switching control mechanism 106. The modal mechanism430 receives a control signal from the electronic device, as indicatedby the incoming arrow 116.

The comparing mechanism 432 includes a resistive divider represented bytwo resistors 502 and 504 connected in series between the second DCsignal provided by the DC-DC mechanism 104 and ground 506. The feedbacksignal 508 to the switching control mechanism 106 is output from acomparator 503, which is connected on its negative input between theresistors 502 and 504, and on its positive input to a reference voltage501. A signal 510 from the modal mechanism 430 is also input between theresistors 502 and 504. Thus, the comparator 503 compares the voltage atthe point between the resistors 502 and 504 to the reference voltage501, and outputs the signal 508 based thereon.

The modal mechanism 430 includes a resistor 512 and a capacitor 513connected in series between the second DC signal provided by the DC-DCmechanism 104 and a transistor 514. In another embodiment, additionalresistors, inductors, and/or capacitors, or a combination thereof, maybe connected in place of or in combination with the resistor 512 and thecapacitor 513. The transistor 514 is itself connected to the signal 510and the control signal received from the electronic device, as indicatedby the incoming arrow 116. When the control signal is not asserted bythe electronic device, the transistor 514 is off. However, when thecontrol signal is asserted by the electronic device, the transistor 514is on. The resistor 502 of the comparing mechanism 432 is thuseffectively connected in a dynamic parallel combination with theresistor 512 and the capacitor 513 of the modal mechanism 430 when thetransistor 514 is on in the low-power mode. The modal mechanism 430effectively skews the comparison performed by the comparing mechanism432, or, put another way, effectively modifies the DC signal as comparedby the comparing mechanism 432. The capacitor 513 is the reactiveelement of the modal mechanism 430, and effectuates the skewing of thesecond DC signal.

FIGS. 6A and 6B show an electronic device 600, according to varyingembodiments of the invention. In FIG. 6A, the power supply 100 that hasbeen described is internal to the electronic device 600, and in FIG. 6B,the power supply 100 is external to the electronic device 600. In bothFIGS. 6A and 6B, the power supply 100 is connected to a power source112, and converts the first AC signal to the second DC signal for use bycomponents 602 of the device 600 in performing the intendingfunctionality of the electronic device 600.

The components 602 are thus those components that enable the electronicdevice 600 to perform an intended functionality. For example, thecomponents 602 may include an image-forming mechanism, such as aninkjet-printing mechanism or a laser-printing mechanism, such that theelectronic device 600 is an image-forming device like an inkjet-printingdevice or a laser-printing device. The intended functionality in thisexample is image formation on media. The components 602, and as a resultthe electronic device 600, when actively operating and performing theintended functionality, cause the power supply 100 to operate in afull-power or a normal-power mode, as has been described. When idling,the components 602, and as a result the electronic device 600, cause thepower supply 100 to operate in a low-power mode, as has also beendescribed.

CONCLUSION

It is noted that, although specific embodiments have been illustratedand described herein, it will be appreciated by those of ordinary skillin the art that any arrangement calculated to achieve the same purposemay be substituted for the specific embodiments shown. This applicationis intended to cover any adaptations or variations of the disclosedembodiments of the present invention. Therefore, it is manifestlyintended that this invention be limited only by the claims andequivalents thereof.

1. A power supply comprising: a conversion mechanism to controlconversion of a first direct current (DC) signal to a second DC signalby switching the first DC signal to vary a voltage of the second DCsignal between first and second voltage levels; and, a feedbackmechanism to cause the conversion mechanism to switch operation betweena nominal-power mode and a reduced-power mode according to a controlsignal, the feedback mechanism comprising a skewing mechanism to skewcomparison of the voltage of the second DC signal between third andfourth voltage levels different than the first and second voltage levelsin response to receiving the control signal.
 2. The power supply ofclaim 1, wherein in the nominal-power mode the conversion mechanism iscaused to switch the first DC signal at least one of a greater dutycycle and at a greater frequency as compared to the duty cycle and thefrequency at which the first DC signal is switched within thereduced-power mode.
 3. The power supply of claim 2, wherein the feedbackmechanism further comprises: a comparing mechanism to compare thevoltage of the second DC signal to the third voltage level and thefourth voltage level and to generate a feedback signal in responsethereto to cause the conversion mechanism to switch the first DC signallow upon the voltage of the second DC signal reaching the third voltagelevel so that the voltage of the second DC signal decreases and toswitch the first DC signal high upon the voltage of the second DC signalreaching the fourth voltage level so that the voltage of the second DCsignal increases, wherein the modal mechanism is to skew comparison ofthe voltage of the second DC signal to the third voltage level and thefourth voltage level in response to receiving the control signal, suchthat the comparing mechanism is effectively caused to compare thevoltage of the second DC signal provided to the electronic device to thefirst voltage level and the second voltage level to switch the first DCsignal low upon the voltage of the second DC signal reaching the firstvoltage level so that the voltage of the second DC signal decreases andto switch the first DC signal at the duty cycle upon the voltage of theDC signal decreasing to the second voltage level so that the voltage ofthe second DC signal increases.
 4. The power supply of claim 3, whereinthe modal mechanism is to pass through the second DC signal to thecomparing mechanism without modification to allow the conversionmechanism to operate in the nominal-power mode, and is to modify thesecond DC signal before passing the second DC signal to the comparingmechanism to cause the conversion mechanism to operate in thereduced-power mode.
 5. The power supply of claim 4, wherein the modalmechanism is to pass through to the comparing mechanism the second DCsignal without modification in absence of assertion of the controlsignal, and is to modify the second DC signal before passing the secondDC signal to the conversion mechanism upon assertion of the controlsignal.
 6. The power supply of claim 2, wherein in the nominal-powermode the second DC signal is regulated.
 7. The power supply of claim 1,wherein in the nominal-power mode an electronic device receiving thesecond DC signal is actively functioning, and in the reduced-power modethe electronic device is idling.
 8. The power supply of claim 1, furthercomprising: an AC-DC mechanism to receive an alternating current (AC)signal from a power source and to convert the AC signal to the first DCsignal; and, a DC-DC mechanism to convert the first DC signal to thesecond DC signal by switching the first DC signal high and low and whichis controlled by the conversion mechanism, and to provide the second DCsignal to an electronic device.
 9. The power supply of claim 1, whereinthe power supply is external to an electronic device receiving thesecond DC signal.
 10. The power supply of claim 1, wherein the powersupply is internal to an electronic device receiving the second DCsignal.
 11. The power supply of claim 1, wherein an electronic devicereceiving the second DC signal is an image-forming device.
 12. A powersupply comprising: a switching control mechanism to control conversionof a first direct current (DC) signal to a second DC signal provided toan electronic device by switching the first DC signal to vary the secondDC signal; a comparing mechanism to compare a voltage of the second DCsignal provided to the electronic device to a first voltage level and asecond voltage level and to cause the switching control mechanism toswitch the first DC signal low upon the voltage of the second DC signalreaching the first voltage level so that the voltage of the second DCsignal decreases and to switch the first DC signal high upon the voltageof the second DC signal reaching the second voltage level so that thevoltage of the second DC signal increases; and, a modal mechanism topass through the second DC signal to the comparing mechanism withoutmodification in absence of assertion of a control signal by theelectronic device to cause the switching control mechanism to operate ina normal-power mode, and to modify the second DC signal before passingthe second DC signal to the comparing mechanism upon assertion of thecontrol signal by the electronic device to cause the switching controlmechanism to operate in a low-power mode.
 13. The power supply of claim12, wherein the normal-power mode is in which the switching controlmechanism is caused to switch the first DC signal at a duty cycle suchthat the voltage of the second DC signal fluctuates between the firstvoltage level and the second voltage level.
 14. The power supply ofclaim 13, wherein the low-power mode is in which the switching controlmechanism is caused to switch the first DC signal at the duty cycleuntil the voltage of the second DC signal reaches a third voltage leveldifferent than the first voltage level and then is caused to lessenswitching the first DC signal until the voltage of the second DC signaldecays to fourth voltage level different than the second voltage level.15. The power supply of claim 12, wherein in the normal-power mode theelectronic device is actively functioning, and in the low-power mode theelectronic device is idling.
 16. The power supply of claim 12, furthercomprising: an AC-DC mechanism to receive an alternating current (AC)signal from a power source and to convert the AC signal to the first DCsignal; and, a DC-DC mechanism to convert the first DC signal to thesecond DC signal by switching the first DC signal high and low and whichis controlled by the switching control mechanism, and to provide thesecond DC signal to the electronic device.
 17. The power supply of claim12, wherein the electronic device is an image-forming device.
 18. Apower supply comprising: a switching control mechanism to controlconversion of a first direct current (DC) signal to a second DC signalprovided to an electronic device by switching the first DC signal tovary the second DC signal; and, means for causing the switching controlmechanism to switch operation between a full-power mode and a low-powermode according to a control signal received from the electronic device,the low-power mode in which the switching control mechanism is caused toswitch the first DC signal at a duty cycle until a voltage of the secondDC signal reaches a first voltage level and then is caused to lessenswitching of the first DC signal until the voltage of the second DCsignal decays to a second voltage level, the means skewing comparison ofthe voltage of the second DC signal between third and fourth voltagelevels different than the first and second voltage levels in response toreceiving the control signal.
 19. The power supply of claim 18, whereinthe full-power mode is in which the switching control mechanism iscaused to switch the first DC signal at the duty cycle such that thevoltage of the second DC signal fluctuates between a third voltage leveland a fourth voltage level.
 20. The power supply of claim 18, whereinthe electronic device is an image-forming device.
 21. An electronicdevice comprising: one or more components to perform a predeterminedfunctionality of the electronic device; and, a power supply to convert afirst direct current (DC) signal to a second DC signal to power the oneor more components, the power supply having a low-power mode in whichthe first DC signal is switched at a duty cycle until a voltage of thesecond DC signal reaches a first voltage level and then lessensswitching of the first DC signal until the voltage of the second DCsignal decays to a second voltage level, wherein the power supply is toskew comparison of the voltage of the second DC signal between third andfourth voltage levels different than the first and second voltage levelsin response to receiving the control signal.
 22. The electronic deviceof claim 21, wherein the predetermined functionality is image formationon media, such that the electronic device is an image-forming device.23. The electronic device of claim 21, wherein the power supply furtherhas a full-power mode in which the first DC signal is switched at theduty cycle such that the voltage of the second DC signal fluctuatesbetween a third voltage level and a fourth voltage level.
 24. Theelectronic device of claim 23, wherein the one or more components asserta control signal to cause the power supply to operate in the low-powermode, and de-assert the control signal to cause the power supply tooperate in the full-power mode.
 25. The electronic device of claim 23,wherein in the full-power mode the one or more components are activelyperforming the predetermined functionality, and in the low-power modethe one or more components are idling.
 26. A method comprising:converting a first direct current (DC) signal to a second DC signal,providing the second DC signal to an electronic device; in response toreceiving a first control signal from the electronic device to operatein a low-power mode: switching the first DC signal at a duty cycle untila voltage of the second DC signal reaches a first voltage level;lessening switching of the first DC signal until the voltage of thesecond DC signal decays to a second voltage; and, skewing comparison ofthe voltage of the second DC signal between third and fourth voltagelevels different than the first and second voltage levels.
 27. Themethod of claim 26, further comprising initially receiving the firstcontrol signal from the electronic device to operate in the low-powermode.
 28. The method of claim 26, further comprising idling by theelectronic device in the low-power mode.
 29. The method of claim 26,further comprising, in response to receiving a second control signalfrom the electronic device to operate in a normal-power mode, switchingthe first DC signal at the duty cycle so that the voltage of the secondDC signal fluctuates between a third voltage level and a fourth voltagelevel, until the first control signal is again received from theelectronic device to operate again in the low-power mode.
 30. The methodof claim 29, further comprising actively functioning by the electronicdevice in the normal-power mode.